Gas expanded rubber



Dec. 6, 1938.

F. w. PEEL GAS EXPANDED RUBBER 2 Sheets-Sheet 1 Filed 901;. 15, 1955 ATTORNEY.

Dec. 6, 1938. w PEE 2,138,877

GAS EXPANDED RUBBER ATTORNEY.

Patented Dec. 6, was I amen UNI-TED STATES PATENT @FFWE GAS EXPANDED RUBBER Frederick w. reel, Redford, va, assignor a Rubatex Products, Inc., New York, N. Y a corporation of Delaware application Qctober 15, 1935, Serial No. 45,4l51

3 fillaims. (Cl. 18-53) My invention relates to novel methods of and Figure 2 is a sectional view along 2- 2, showmeans for gassing rubber dough in the manufacing the construction of the perforated plunger;

ture of expanded rubber. Figure 3 is a sectional drawing showing the as The manufacture of expanded rubber consists sembly for increasing the acoustic absorption of in thoroughly impregnating a suitable rubber gas expanded rubber applied to a ceiling; mixture with an inert gas at very high pressure Figure 4 ws a portion of the Ceiling and subsequently heat treating the gassed mix-l structlon- 'ture for final expansion and vulcanization. Such y n Out y invention, e following i a process is the basis of the Denton patents, such gredients y b used to make the rubber 1111K- as U. s. Patent No. 1,905,269, dated April 25, 1933, ture in h indic t d proportions by weight:

and the co-pending U. S. application Serial No.

717,550: a 27, we of which I am a 151222 55155;aatgauiiji 1122: 332'. mventor- T e r sh gas pressure is applied in an Lithophnne 3lbs 0 m autoclave a d is 0f the order of 150-200 atmos- Parafiin 1m 8 on pheres. The gassing chamber is, therefore, nec- Zinc Oxide 1m 3 oz. essarily an expensive apparatus. The rubber that sulphur 2 lbs, 4 O1 is 1 0 be gassed under this high pressure has to be ,mphenylguanidine 4 5% p p red and placed in a vehicle which makes Agerite 8 OZ, it P s e l ll] t0 be handled in and 0111'; Of the Carbon k 11 GK gassing chamber. '1 lerefore, the preparation i and machinery required, plus the labor, makes Reasolllable Changes in these P P Or in such a process very expensive. the speclfied components are entirely feasible.

11 .13, accgrdingly an object of my invention to The ingredients are individually mixed on the break down the rubber to such a plastic forzn that B1111 m a manner Pl E the art rubber 9 it will be possible to impregnate this dough witlh compounding The mdlvfdufl shfegbs of rubber t inert gas Without the use of a high pressure are masticated'or softened into a single soft mass chambe; by masticating rollers which are heated to a tem v It is another object of my invention to provide 3x32 a; 3 g 52:2 E si g 1 22 means for mlxmg the dough Wlth the mm identified application, Serial 210;!17550.

It is still another object of my invention to rendelbthe i g g ii g provide a novel method of preventing the gassed W P0551 18 t0 lmitleena e e W1 hlbber dough from 1051man M the after inert gas, add approximately gallons of carbon the passing stage a y g tetrachloride and place the whole into the cylin- It is a further object of my invention to provide s ii gi g gg g 23%: i i i gf g fi g g J i gggi-gggfgi g iigi gg f t rubber about three times that of the total volunie of this mixture. 1

It is still a further object of my invention to The apparatusl illustrate m Figure lfor carry provide a novel gas expanded rubber that is nonmg out the gas mixing stage f my invention -20 m I sists essentially of a cylindrical drum m which It lsanother ob ect of my invention to provide contains the plunger M at the end 33 of/the rod a novel application for the gas expanded rubber m This plunger 53 has l ralit i ho ad i Of y invention increase its ac u t drilled through it, as clearly illustrated in Figabsorption properties. me These and other objects of my'inventicn will After the mixture 29 oi'rubber dough and carbecome apparent in connection with the descripbon tetrachloride is placed in the drum it, the

tion to follow and the drawings, in which:- gas-tight lid i5 is clamped on the drum ill with Figure 1 is a sectional elevation of the mixing bolts lb. The nitrogen is admitted to the drum apparatus; p it through the pipeline 3? at relatively low pres 5O sure. The pressure gauge 18 and valve I! are shown connected to the pipe line l1. Nitrogen at about 100 lbs. pressure is applied to the interior of the drum. The plunger II is then caused to reciprocate vertically through the mixture 20 by connecting suitable mechanical means, not shown, to the other end 13' of the rod l2. The perforated plunger ll causes the rubber dough and the carbon tetrachloride solution to amalgamate homogeneously and the gas to be impregnated throughout the mass, resulting in a rubber froth. This process is continued for about two hours.

To maintain this froth intact, the resulting mass is poured into very hot molds in order to form a skin around it. This skin is formed in a few seconds and prevents the escape of any confined nitrogen. I provide an outlet line 2| with a valve 22 to conduct the rubber froth from the drum II] to the molds. Subsequent to' the skin formation at the relatively high temperature, the temperature of the molds is then reduced and permitted to remain this way until the rubber is finally cured.

The following is an alternative method for producing gas expanded rubber with the use of my apparatus. The rubber dough is prepared in a manner similar to that described hereinabove ex-' cept that the sulphur and the diphenylguanidine accelerator are omitted and a little additional softener, such as stearic acid or reogen, is added. The dough is prepared to a consistency of thick grease. This dough in a warm state is placed into the drum l0 and the lid I5 is clamped thereon. Nitrogen at about 25 pounds per square inch pressure is then admitted. The plunger H is reciprocated to cause the dough to adsorb the nitrogen gas, and this is continued until the dough and the gas are homogeneously beaten together. The necessary sulphur and accelerator (-diphenylguanidine) are then forced into the froth with the aid of the reciprocating plunger II. The dough is then forced into the heated molds and is finally cured.

The introduction of carbon tetrachloride to the mixture renders the gas expandedrubber product non-inflammable. The property of an expanded rubber that it will not burn is an advantage for such a product, which, although not a primary object ofmy invention, is a result thereof due to the use of carbon tetrachloride as the amalgamatlng agent in the gas impregnating stage. 7

The rubber froth produced as hereinabove set forth, may be vulcanized and expanded to final form in a manner similar to the die-casting of particular metal alloys well known in the mechanical arts. The froth is forced through bleeders which communicate into a plurality 'of molds. These molds may have complicated forms. The necessary heat is applied to the molds by means of steam coils arranged about them or by enclosingsteam chambers about the molds. The steam heat causes the gassed rubber to expand and fill every crevice of the mold, and finally cures or vulcanizes the rubber. The myriad of gas cells are smalland independent of each other. The molds must be cooled before removed, to prevent the gas cells in the heated rubber from bursting. The steam is accordingly shut ofi and cold water is accordingly circulated in place of the steam. The completed molds are then removed. This is a cheap, quick and efficient process for producing gas expanded rubber products of simple or complicated shapes.

The gas expanded rubber product of my invention may be made up into solid boards and these .sonable thickness.

boards have marked acoustic absorbing properties comparable to other well-known acoustic board materials. Although these boards may be utilized in any well-known manner for their acoustic characteristics, I have indicated in Figures 3 and 4 their application in a novel manner to further increase their acoustic absorption properties by as much as 40%. I

In Figure 3 I have shown such gas expanded boards 23 suitably attached to wooden ceiling planking 24. Spaced from the rubber boards 23 by Celotex or balsa wood spacers 25 are gas expanded rubber blocks 26, mounted as indicated in Figures 3 and 4. Wood screws 21 hold the rubber blocks 26 in position. These screws 21 pass through the respective corners 28 of the rubber blocks 26, through the balsa wood spacers 25, through the rubber boards 23, and onto the celling planking 24. Fiber washers 29 may be placed under the head of the screws 21. The rubber blocks 26 may well be 1 foot square and of rea- These'blocks 26 have a plurality of holes 30 formed through them. The blocks 26 are spaced from each other, as indicated in Figure 4, and form a regular ceiling pattern.

The sound waves impinging on this ceiling construction will first impinge upon the surface of the acoustic rubber blocks 26 where a great percentage of the sound is absorbed. The sound pressure waves also pass through the holes 30 and spaces 31 and another percentage of the sound is absorbed along the surfaces encountered therethrough. The remaining sound pressure waves enter the relatively confined air spaces 32 and impinge upon the surfaces 33 of the rubber boards 23. The remainder of the sound energy is ab-' sorbed in this region. This method of construction is not intended solely for ceilings but may be applied in general for improved acoustic absorption. Similarly, this method of construction may equally well be utilized with acoustic absorbing materials other than the rubber blocks 26 and rubber boards 23.

Although I have described in detail a preferred embodiment ,of apparatus which I use in gas impregnating the rubber according to my invention and although I describe specific constituents of the mixture and preferred steps for its production, it will be obvious that modifications still coming within the scope of my invention may be made as to the constituents, the steps in the process, andin the apparatus therefor, and I do not intend to be limited except by the appended claims.

I claim: 7

1. The method of manufacturing gas expanded cellular rubber which comprises vigorously agitating a rubber solution in the presence of nitrogen at a pressure of the order of 25 to pounds per square inch to form a cellular rubber froth, pouring the cellular rubber froth into a mold heated to a temperature above that necessary to vulcanize the rubber to form a skin on the rubber froth so as to prevent escape of gas contained therein and reducing the initial temessary to vulcanize the rubber to form a skin 011 7 the rubber froth so as to prevent escape of gas contained therein and reducing the initial temperature of the mold to completely and uniformly vulcanize the gas expanded cellular rubber.

3. The method of manufacturing gas expanded cellular rubber which comprises forming a rubber solution; agitating the rubber solution vigorously in the presence of an inert gas under low pressure to form a cellular rubber structure;

passing the gassed cellular rubber to a mold heated to a temperature above that necessary to vulcanize the rubber so as to form a skin on the cellular rubber structure in the mold so as to prevent the escape of the gas contained therein and; reducing the initial amount of heat applied to the cellular rubber to completely and uniformly vulcanize the gas expanded cellular rubber.

FREDERICK W. PEEL. 

